Spectrum Management System For Municipal Spectrum Using Guided Cognitive Radio

ABSTRACT

Described is a system and method for assigning a frequency to an access point in a wireless network comprising a plurality of access points. The system and method includes accessing a rule-base to obtain a set of rules for the wireless network, accessing a license database to obtain information about relevant wireless nodes in a region, creating a list of possible primary node frequencies from a list of frequencies associated with primary wireless nodes in the license database, creating a list of possible secondary node frequencies from a list of frequencies associated with secondary wireless nodes in the license database, identifying a list of clear frequencies from a set of unused frequencies, selecting a frequency from frequencies in the lists of possible primary node frequencies, possible secondary node frequencies, and clear frequencies and registering the frequency in the license database.

BACKGROUND

The electromagnetic spectrum is a limited resource. In the UnitedStates, the Federal Communication Commission (FCC) is responsible forallocating the bandwidth of the electromagnetic spectrum. Specifically,the Communications Act of 1934 established the FCC and gave the FCC abroad grant of power to regulate spectrum “in the public interest.” TheFCC is constantly working to ensure that the electromagnetic spectrum isallocated and assigned in a manner that minimizes or eliminatesinterference so that the American people receive the maximum benefits ofwireless technologies and services.

A number of the frequency bands in the electromagnetic spectrum areassigned for unlicensed “open use” wherein multiple differentbroadcasters and receivers use the same frequency range forcommunication. The sharing is generally accomplished by limiting thebroadcast power such that only receivers within a small area around atransmitter will be able to receive the broadcast. As long as differenttransmitters are not located within the same area, there will be nointerference between the different users of the same frequency band.

With consumers purchasing large numbers of such unlicensed open usewireless equipment, interference between devices is becomingincreasingly common. This problem is especially acute in urban areas.Thus, it would be desirable to have other methods of sharing a commonfrequency band in a more organized and more efficient manner.

SUMMARY OF THE INVENTION

A method for assigning a frequency to an access point in a wirelessnetwork comprising a plurality of access points. The method includesaccessing a rule-base to obtain a set of rules for the wireless network,accessing a license database to obtain information about relevantwireless nodes in a region, creating a list of possible primary nodefrequencies from a list of frequencies associated with primary wirelessnodes in the license database, creating a list of possible secondarynode frequencies from a list of frequencies associated with secondarywireless nodes in the license database, identifying a list of clearfrequencies from a set of unused frequencies, selecting a frequency fromfrequencies in the lists of possible primary node frequencies, possiblesecondary node frequencies, and clear frequencies and registering thefrequency in the license database.

A broadband wireless network system, the broadband wireless networksystem including a wired network, a rule-base, the rule-base comprisinga set of rules for the wireless network, a license database, the licensedatabase comprising information about all relevant wireless nodes in aregion and a plurality of access points, the access points coupled tothe wired network, each of the access points executing a guidedcognitive radio assignment program for selecting an operating frequency.

An access point comprising a memory storing a set of instructions and aprocessor to execute the set of instructions. The set of instructionsbeing operable to access a rule-base to obtain a set of rules for thewireless network, access a license database to obtain information aboutrelevant wireless nodes in a region, create a list of possible primarynode frequencies from a list of frequencies associated with primarywireless nodes in the license database, create a list of possiblesecondary node frequencies from a list of frequencies associated withsecondary wireless nodes in the license database, identify a list ofclear frequencies from a set of unused frequencies, select a frequencyfrom frequencies in the lists of possible primary node frequencies,possible secondary node frequencies, and clear frequencies and registerthe frequency in the license database.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B and 1C illustrate a high-level flow diagram that sets forthsteps that an access point may follow to join a guided cognitive radiosystem according to the teachings of the present invention.

DETAILED DESCRIPTION

The present invention may be further understood with reference to thefollowing description and the appended drawings, wherein like elementsare referred to with the same reference numerals. The exemplaryembodiment of the present invention describes a system and a method forclassification of network traffic to classify a network entity inadvance of an impact thereof on a network. A classification of theentity determined as a function of a response generated as a result of astress test performed thereon, as will be described below.

Overview of Metropolitan Area Networks.

Many cities have realized the value of unified wireless broadband packetaccess to citizens, municipal workers, and emergency responders.“Metropolitan Area Networks” or MANs (e.g. 802.16/WiMAX) can providesuch wireless broadband data communication service, but because of theirlarge-cell architecture, eventually become incapable of supplyingsufficient throughput per user. Fourth-generation (4G) small-cellsystems divide their maximum throughput over a much smaller area, andhence offer much higher throughput per user. Such “Neighborhood AreaNetworks” (NANs) can reuse spectrum much more densely, and as a resultcan also utilize spectrum more efficiently.

A number of cities have begun using pre-4G WiFi hardware to pioneerbroadband “Digital City” access concepts in order to bridge the “DigitalDivide” (lack of internet access by the disadvantaged), lower municipalcommunications costs, and provide a source of revenue as a digitalcommunication utility. These early manifestations have attempted tocapitalize upon unlicensed spectrum such as ISM or U-Nil bands foroutdoor service, leveraging the success systems such as WiFi have hadindoors.

Although workable for best-effort data traffic, use of unlicensed bandsforces the system to contend with interference controlled only byFCC-prescribed device emission limits. Uncontained by building walls,emissions travel further outdoors, increasing interference potentialfrom a variety of sources. As municipal systems mature and traffic growsto become more multimedia rich, interference will eventually limit theability to provide reliable communications and Quality of Service (QoS)for streaming services just as citizens and city employees begin todepend on it. The prospect jeopardizes investment in Digital Citywireless infrastructure.

As a result of municipality concerns regarding the expenditures forearly Digital City implementations, examination of spectrum options hasbecome an important topic. The topic has ignited revisitation ofbroadband telecommunications policy at the Federal level and newspectrum regulations by the FCC. A particularly rich area of discussionhas been the concept of a spectrum “Commons” where a group of users maybe licensed to use a block of spectrum for designated uses (rather thanparticular devices, as with the ISM and U-NII bands). Such a spectrumcommons requires some type of system of mediating access to the spectrumbetween the various users.

Cognitive Radio

To efficiently mediate the use of spectrum, the technology of “CognitiveRadio” may be used. Cognitive radio technology uses a combination ofcomputerized intelligence and frequency-agile radio receivers to examineprospective spectrum for a radio service by conducting an examination offrequencies in the band where the equipment is capable of operating.Following the survey of the frequency band, cognitive radio softwareattempts to categorize received emissions according to type andsubsequently determines if particular channels in the frequency bandcould be used by the node without causing troublesome interference toexisting users.

As a matter of practice, most emerging cognitive radio implementationsdo not use information to provide “initial conditions” for the channelsearch, other than the frequency band allocation itself. Althoughcognitive radio is an exciting prospect, the degree of artificialintelligence required to properly survey, interpret, and categorize allof the collected information and then estimate interference potentialmay be considerable. Consequently, the wide use of cognitive radiotechnology without sufficient operating experience should not beundertaken as it could hazard many services which might share commonspectrum.

To remedy problems within existing cognitive radio technology, thepresent invention proposes a novel system using a combination of“guided” cognitive radio. Specifically, guided cognitive radio is usedin combination with a secure database and an “automatic licensing”server to reduce the possibility that an uncontrolled cognitive radiosystem could misbehave and thus damage the value of an entire frequencyband. In this manner, a cognitive radio system that efficiently mediatesfrequency band usage may be safely deployed.

The system of the present invention has been innovated in conjunctionwith a companion “Municipal Spectrum” regulatory concept that hasrecently been exposed to the FCC, a group of Public Utility Commissions,and several cities entertaining plans of converting to the utility modelfor broadband wireless access. The municipal spectrum concept will bedisclosed as one possible implementation of the teachings in thisdocument in order to illustrate how the proposed spectrum managementsystem would work. However those skilled in the art will recognize thatthe idea can be applied to other spectrum mediation situations.

In one municipal spectrum implementation of the present invention, it isrecommended that cities apply for Digital City status and be grantedsecondary user status in the existing 6 GHz microwave relay band. In the6 GHz microwave relay band, primary users are licensed to operatepoint-to-point microwave relays between fixed, geographically designatedpoints at specified power levels and with specified antennaconfigurations. The municipal spectrum system having secondary userstatus should operate without interfering with the primarypoint-to-point licensees.

It should be noted that Secondary use status already has a precedent inFCC-regulated bands and many such secondary services have already beendesignated. These services must cease operation if they causeinterference to the primary licensed operations. However, experience hasshown that primary and secondary uses can cooperate in the same spectrumband if their uses and architectures are disparate enough to minimizeinteractions.

The envisioned benefit of municipal spectrum system as described hereinwould accrue only to registered cities that would be granted secondarylicense status if they apply for Digital City operation. A particularinstantiation of a Digital City 4G network could be, for example, the“HomeRun” system innovated by AT&T. In the HomeRun system, outdoorcoverage is established by a network of outdoor access points thatilluminate areas up to a radius of approximately 1000 feet. Within thecoverage area, links can be close to outdoor mobile devices and to“window bridges” installed within premises that join self-organizedindoor networks to the outdoor network. With the proposed municipalspectrum implementation, the outdoor portion of such an indoor/outdoorwireless broadband service is proposed to operate in the 6 GHz band (itcurrently operates at the high frequency end of the Unlicensed-NII bandat near 5.8 GHz). The frequency displacement is sufficiently small toallow current radio architectures and integrated circuit designs to makethe transition with few modifications.

Cognitive radio is essentially a substitute for human coordination ofspectrum. The ‘guided cognitive radio’ system of the present inventionproposes an intermediate step between a manual spectrum managementprocess and a completely artificial-intelligence (AI) based spectrummanagement process. A major value component of the “guided” cognitiveradio concept (aside from safely accumulating experience with thetechnique) is that the automated spectrum management approach of guidedcognitive radio makes control of small-cell architectures moreeconomical. Furthermore, the guided cognitive radio system ensures thatmunicipalities are provided some protection from interference whereasthis is generally not available to unlicensed operation outdoors. Theautomated spectrum management is a necessary improvement, since 4G NANsystems may utilize more than 100 small cells to serve the same areacovered by one 3 Km. MAN cell.

The guided cognitive radio system of the present invention utilizes astored program resident on an outdoor access point outfitted to utilizemunicipal spectrum. Each access point contains either a GlobalPositioning Service (GPS) device or geographic location coordinatesprogrammed at the time of its installation (if the access point isfixed) so the exact location is known by the access point's program. Theprogram executes six functions: municipal rule-base download, spectrumassay, secure database access, propagation modeling, secure licenseregistration, and municipal access point status notification.

The access point software works in concert with a municipal systemserver, a license database server and a license registration server, allof which are coupled with a data communication network. The datacommunication network may be a broadband packet network such as theInternet. The latter two servers may be combined into a single facility.FIGS. 1A, 1B and 1C illustrate a high-level flow diagram that sets forththe steps that an access point may follow in one embodiment of thepresent invention in a municipal spectrum system.

Initially, an access point is installed at step 110. As set forth, theinstallation requires a connection to a wired data communicationnetwork. Following the mechanical and electrical installation, anewly-connected outdoor access point uses its network connection toestablish contact with a secure municipal system server to begin theprocess of integrating itself into the municipal spectrum system. Theaccess point downloads an operations rule-base from the secure municipalsystem server as set forth in step 113. Ideally, this download isperformed using a secure communication means such as IPSec. Theoperations rule-base downloaded from the secure municipal system serverprovides the Access Point with policies for the municipal system such asexcluded frequencies, reserved frequencies, common pool frequencies,maximum power allowances, and other system operating information for themunicipal system.

Next, the access point contacts the regional license database server.This regional license database may be maintained by the FederalCommunication Commission (FCC) or by a nominated private agent. Theregional license database contains detailed information about all theprimary (point-to-point relay) and secondary (municipal) radio nodes inthe area. The information may include by is not limited to geographiclocations as well as heights, frequencies, bandwidths, emission types,power levels, and antenna configurations. Special annotations may alsobe provided to indicate that no secondary operation must occur oncertain frequencies within a minimum distance, as might be the case formilitary (e.g. radar), governmental, scientific, or other primarycommercial applications (e.g. carrier network-related). The access pointdownloads this information about all the local radio nodes as set forthin step 115. As with the connection to the municipal system server, thisdownload is ideally performed using a secure communication means such asIPSEC.

After obtaining information from both the municipal system server andthe regional license database, the access point then conducts a spectrumassay using its radio hardware as set forth in step 120. The spectrumassay is initially performed on the database-listed frequencies andsubsequently on other frequencies marked for use. Note that somefrequencies may be marked as excluded by the local municipal rule-base.

For each primary-license node in the license database, the access pointuses a propagation model program to estimate how the signals associatedwith that node's frequency will behave. Specifically, the access pointsupplies the access point's own geographic location along with thegeographic location and characteristics of that primary-license radionode to the propagation model program to estimate the radio loss betweenthe two nodes as set forth in step 130. The propagation model may takeinto account local topography (e.g. downloaded topographic map data),distance, spreading, diffraction, and other attenuation effects.

The result of the propagation model's operation is an estimation of theloss in dB that may be expected to isolate operations between the tworadio nodes on that primary-license node's frequency. If no specialannotations are present for that frequency or node and the rule-baseminimum isolation value is not exceeded then that particular frequencymay be marked for “cooperation-primary” use and is placed, in an orderedfrequency/node list as set forth in step 133. Steps 135 and 137 ensurethat steps 130 and 133 are applied to every primary license nodeobtained from the regional license database. Finally, the frequency/nodelist entries are ordered by isolation value with highest isolation firstas set forth in step 139.

Next, at step 140, the access point begins to tune into to eachfrequency in the created frequency/node list to test the differentvarious frequencies that may be used. In particular, the noise level onthe frequency is tested. If the noise on the frequency exceeds arule-base threshold level then that node/frequency entry is removed amthe frequency list as set forth in step 141. This removal is done on theassumption that extraordinary propagation effects not taken into accountby the propagation model may be present. The access point thendetermines if the node/frequency entry falls within the parameters of aminimum distance exclusion rule used to keep radio nodes that use thesame frequency a minimum distance apart. Those node/frequency entriesthat violate the minimum distance exclusion rule are removed from thelist as set forth in step 143. Steps 145 and 147 ensure that steps 140,141, and 143 are applied to every node/frequency entry in thefrequency/node list. Finally, at step 149, the access point reorders thenode/frequency list according to measured noise level with the smallestmeasured noise level first.

The access point then utilizes a propagation model to similarly examineinterference potential to other municipal secondary-licensed accesspoints that are already part of the license database as secondary-uselicenses as set forth in step 150. The propagation model may be the sameused in the earlier steps concerning primary licensees or anotherpropagation model more appropriate for small cell, low antenna heightPTMP municipal networks. As before, the propagation model usesgeographic locations of the access point and the other secondary-licenseaccess point to estimate attenuation between the two nodes. This testdiscloses other municipal network nodes in the area that may be isolatedsufficiently (i.e. below the rule-base threshold for secondary use) andthat the frequencies upon which they operate can be reused with nosignificant interference. Similarly, these frequencies that can beisolated sufficiently are then added to a “cooperation-secondary”node/frequency list as set forth in step 153. At step 159, the secondarynode/frequency list is ordered by isolation value with the highestisolation value first.

The access point then tunes to each frequency in the secondarynode/frequency list as set forth in step 160. If noise on a particularfrequency exceeds the secondary rule-base threshold, the channel entryis removed as set forth in step 161. Similarly, if any rule-baseconstraints obtained from the municipal server such as minimum distanceapply then that node/frequency is also removed from the secondarynode/frequency list as set forth in step 163. Finally, the access pointreorders the secondary node/frequency list according to measured noiselevel with the smallest noise level first as set forth in step 169.

The access point then creates a list of frequencies that are within theband but not part of the excluded or reserved lists downloaded from themunicipal server or not currently listed in the regional licensedatabase as set forth in step 160. Since there is no geographic locationinformation for these frequencies that identifies a transmissionorigination point, the access point cannot measure interferencepotential using a propagation model. Instead, the access point can onlytune into the unused frequencies and measure the signal properties asset forth in step 170. If any frequency appears to show signals from anunregistered (unlicensed) node then the access point may provide thisinformation to the municipal system server as set forth in step 171.However, such a frequency is not marked for potential use. Suchunlicensed emissions may occur due to latency between the licenseregistration and license database servers, or could result from illegaltransmitters or “splatter” due to adjacent frequency front-end overload.At step 173, the access point enters frequencies from the unusedfrequency list that were measured to be below the rule-basesignal-strength threshold into a “clear” frequency list. After testingall of the unused frequencies, the access point then orders the clearfrequency list by noise level with the lowest noise level frequencyfirst as set forth in step 179.

At this point, the access point has collected three groups offrequencies for possible use as part of an organized municipal network:a list of frequencies occupied by licensed primary operations (theprimary node/frequency list), frequencies occupied by licensed secondarynodes (the secondary node/frequency list), and a third listcorresponding to channels not licensed and apparently “clear” (the clearfrequency list).

Next, at step 180, the access point may execute a “self-organization”process particular to the municipal system being installed. An exampleof such a self-organization process is disclosed in a patent issued toM. Benveniste in conjunction with an indoor cellular system. Theteachings of U.S. Pat. No. 6,775,549, Method for self-calibration of awireless communication system, U.S. Pat. No. 6,615,040,Self-configurable wireless systems: spectrum monitoring in a layeredconfiguration, and U.S. Pat. No. 6,259,922, Managing interference inchannelized cellular systems are hereby incorporated by reference intheir entirety.

A self-organization process uses the ordered lists of candidatefrequencies to converge to a sub-optimal frequency assignment for eachparticipating access point in the municipal network. The basicBenveniste process would be modified to use frequencies from the clearfrequency lists, the primary node/frequency list, and the secondarynode/frequency list in that order of preference. Since each individualaccess point in the network has arrives at its own list of validfrequencies, the iterative reuse-optimization process is constrained bythe entries in each access point's frequencies list. If the databaseindicates that one or more access points of the particular system isalready in the database, the implication is that those access points arealready operating. Accordingly, those access points may be assumed tohave already completed at least one self-organization cycle andregistered automatically for licenses. If this is the case, the accesspoint must first coordinate with the local municipal server and possiblythe other access points already in the established network to schedule a“reconfiguration” cycle. Detailed information about this process is setforth in the previously identified Benveniste patent. If there are noexisting municipal (secondary-use) access points already operating, theaccess point contacts the municipal system server and negotiates use ofthe lowest noise frequency on the clear frequency list.

Those skilled in the art will recognize that the self-organizationprocess may be a distributed process or a centralized process. If adistributed process is employed, individual access points would eachcontain a program that would interact with other access points toconverge to a sub-optimal frequency plan. In the case where no othernetwork access points are reachable, the access point would then choosethe lowest-noise frequency from the clear frequency list autonomously.

After an access point has completed the spectrum “examination” and“organization” phases of the process, the access point then performs afinal “registration” phase at step 190. The frequency that the accesspoint will use has been determined by the self-organization algorithm,by recommendation to the municipal system server of the preferred(lowest-noise) “clear” channel, or by autonomously selecting anoperating frequency. The registration phase begins with the access pointcontacting the license registration server. Ideally, the contact isperformed using a secure communication means such as IP-Sec or anothersecurity protocol. The license registration server's function is toimplement a machine-to-machine (M2M) licensing procedure that willcreate a “virtual” license for each access point registering with thecorrect credentials. These credentials may include but are not limitedto a security code that may be installed during access pointinstallation, a geographic location, and the municipal Digital Cityauthorization number. After forwarding this information and obtainingauthentication from the license server, the access point sends itsproposed operating frequency, selected power level, bandwidth, antennaconfiguration, emission type, height, and other information which may belater determined as valuable for coordination.

The license registration server accepts the info nation and stores theinformation in a registered license database. The license registrationserver then issues a certification code to the access point. Thecertification code provides the access point with proof that it isoperating legally and that a “virtual” license has been issued based onthe parameters the access point submitted to the license registrationserver. If the access point is operating in conjunction with a municipalserver then the access point sends the certification code to thatmunicipal server along with the operating information that is linked tothe license.

Subsequently, the license registration server sends the new licenseinformation, using a secure connection, to the license database server.The license database server updates the information accessible to otheraccess points that may subsequently wish to join the wireless network.The license database is also updated when new microwave point-to-pointlinks (primary licensees) are licensed. As a primary licensee, apoint-to-point link installation may impact one or more access points(secondary licensees) that may be located along the boresight path ofthe point-to-point link. This may require a rearrangement of accesspoint frequencies in order to eliminate interference. Such arearrangement would be initiated when the license registration servermarks the database with a “new primary license” indication.

Access points already licensed must periodically coordinate with thelicense database in order to determine if the new information impactsoperation. In one embodiment, each access point may contact the licensedatabase at least twice in each 24 hour period. If operation is impactedthen a frequency reorganization with appropriate system frequencychanges must be initiated immediately following the impactdetermination. In one embodiment, the frequency reorganization isperformed within 1 day. Furthermore, the reorganization should beperformed when the system is minimally used. The Benvenisteself-organization process contains a method for accommodating suchchanges while connections/sessions are in progress.

In one preferred embodiment, each access point may also be outfittedwith the capability for being commanded to shut down its transmitterimmediately by command. Such shut down commands may be sent from themunicipal system server or other server operated by a sanctionedgoverning or regulatory body. This shut-down capability is necessary tomeet the requirement of secondary use that it shall not interfere withprimary use(s) and must be taken off the air if interference occurs.

It will be apparent to those skilled in the art that variousmodifications may be made in the present invention, without departingfrom the spirit or scope of the invention. Thus, it is intended that thepresent invention cover the modifications and variations of thisinvention provided they come within the scope of the appended claims andtheir equivalents.

1.-21. (canceled)
 22. A method for performing a spectrum assay, themethod comprising: receiving a set of frequencies; determining which ofthe set of frequencies exceeds a minimum isolation value; eliminatingthose frequencies exceeding the minimum isolation value from a list ofclear frequencies; determining which of the set of frequencies violatesa minimum distance exclusion rule; and eliminating those frequenciesviolating the minimum distance exclusion rule from the list of clearfrequencies.
 23. The method as set forth in claim 22, furthercomprising: creating a list of possible primary node frequencies from alist of frequencies associated with primary wireless nodes in a licensedatabase.
 24. The method as set forth in claim 23, wherein creating thelist of possible primary node frequencies from the list of frequenciesassociated with the primary wireless nodes in the license databasecomprises: eliminating unsuitable frequencies in the list of frequenciesassociated with the primary wireless nodes in the license database byapplying a propagation model and the set of rules; and eliminatingunsuitable frequencies in the list of frequencies associated with theprimary wireless nodes in the license database by testing the list offrequencies associated with primary wireless nodes and applying the setof rules.
 25. The method as set forth in claim 24, wherein applying thepropagation model and the set of rules comprises eliminating frequenciesthat exceed the minimum isolation value.
 26. The method as set forth inclaim 24, wherein testing the list of frequencies associated with theprimary wireless nodes and applying the set of rules compriseseliminating frequencies that exceed the noise threshold value.
 27. Themethod as set forth in claim 24, wherein testing the list of frequenciesassociated with the primary wireless nodes and applying the set of rulescomprises eliminating frequencies associated with nodes that do notfulfill the minimum distance exclusion rule.
 28. The method as set forthin claim 23, wherein creating the list of possible primary nodefrequencies from the list of frequencies associated with the primarywireless nodes in the license database further comprises: ordering thelist of possible primary node frequencies by isolation value.
 29. Themethod as set forth in claim 23, wherein creating the list of possibleprimary node frequencies from the list of frequencies associated withthe primary wireless nodes in the license database further comprises:ordering the list of possible primary node frequencies by noise level.30. The method as set forth in claim 22, further comprising: creating alist of possible secondary node frequencies from a list of frequenciesassociated with secondary wireless nodes in a license database
 31. Themethod as set forth in claim 30, wherein creating the list of possiblesecondary node frequencies from the list of frequencies associated withthe secondary wireless nodes in the license database comprises:eliminating unsuitable frequencies in the list of frequencies associatedwith the secondary wireless nodes in the license database by applying apropagation model and the set of rules; and eliminating unsuitablefrequencies in the list of frequencies associated with the secondarywireless nodes in the license database by testing the list offrequencies associated with secondary wireless nodes and applying theset of rules.
 32. The method as set forth in claim 31, wherein applyingthe propagation model and the set of rules comprises eliminatingfrequencies that exceed the minimum isolation value.
 33. The method asset forth in claim 31, wherein testing the list of frequenciesassociated with the secondary wireless nodes and applying the set ofrules comprises eliminating frequencies that exceed the noise thresholdvalue.
 34. The method as set forth in claim 31, wherein testing the listof frequencies associated with the secondary wireless nodes and applyingthe set of rules comprises eliminating frequencies associated with nodesthat do not fulfill the minimum distance exclusion rule.
 35. The methodas set forth in claim 30, wherein creating a list of possible secondarynode frequencies from a list of frequencies associated with thesecondary wireless nodes in the license database further comprises:ordering the list of possible secondary node frequencies by isolationvalue.
 36. The method as set forth in claim 30, wherein creating a listof possible secondary node frequencies from a list of frequenciesassociated with the secondary wireless nodes in the license databasefurther comprises: ordering the list of possible secondary nodefrequencies by noise level.
 37. The method as set forth in claim 22,further comprising: accessing a rule-base to obtain a set of rules for awireless network, wherein the set of frequencies is designated by theset of rules.
 38. The method as set forth in claim 22, furthercomprising: determining which of the set of frequencies exceeds a noisethreshold level; and eliminating those frequencies exceeding the noisethreshold level from the list of clear frequencies.
 39. A method,comprising: determining a set of unused frequencies; measuring a signalstrength of each of the unused frequencies; eliminating frequencies inthe set of unused frequencies having a signal strength exceeding asignal-strength threshold value to obtain a set of clear frequencies;and selecting a frequency from the set of clear frequencies and afurther set of frequencies.
 40. The method of claim 39, furthercomprising: sending a message indicating that a signal on at least oneof the unused frequencies is from an unregistered node.
 41. The methodof claim 39, further comprising: ordering the set of clear frequenciesbased on a measured noise level, wherein frequencies having lower noiselevels are ordered first.